As a substrate processing apparatus for manufacturing semiconductor devices, there has been widely employed a parallel plate type plasma processing apparatus having a lower electrode for mounting thereon a substrate such as a semiconductor wafer or a liquid crystal substrate and an upper electrode facing the lower electrode within a processing chamber. In such a plasma processing apparatus, a substrate is mounted on the lower electrode, and a processing gas is introduced into the processing chamber. Then, plasma is generated between the electrodes, and a plasma process such as etching or film formation is performed on the substrate by the plasma.
In such a parallel plate type plasma processing apparatus, since plasma is generated between the electrodes, a surface of an electrode plate of the upper electrode is exposed to the plasma and is worn out, so that a distance between the electrodes is varied (see, for example, Patent Document 1). If the distance between the electrodes is varied too much, such a variation may have an adverse effect on process properties of the substrate. Thus, it is required to replace the electrode plate of the upper electrode at a proper timing.
For the purpose, conventionally, it has been attempted to calculate a consumption amount of consumables such as an electrode plate based on cumulative usage history of the plasma processing apparatus or by using multivariate analysis (see, for example, Patent Document 2). For example, in order to estimate the consumption amount based on the usage status of the plasma processing apparatus, the consumption amount of the consumables has been calculated by measuring an electric discharge time of a high frequency power (RF electric discharge time) applied to the electrode plate. If this RF electric discharge time exceeds a preset threshold value, an alarm has been automatically activated or an instruction for replacing the consumables has been provided to manage the consumables.    Patent Document 1: Japanese Patent Laid-open Publication No. 2003-332314    Patent Document 2: Japanese Patent Laid-open Publication No. 2004-335841
In recent years, however, processing conditions for performing a plasma process have been diversified and environment within a processing chamber has been complicated. Thus, it has been getting difficult to accurately calculate the consumption amount of the electrode plate. Furthermore, since there is an increasing demand for miniaturization of devices formed on a substrate, even a slight variation of a distance between the electrodes may not be neglected.